The present invention relates to a combustor assembly of a gas turbine engine. More specifically, the present invention relates to an apparatus and method of cooling a combustor liner of a gas turbine engine.
A gas turbine engine extracts energy from a flow of hot combustion gases. Compressed air is mixed with fuel in a combustor assembly of the gas turbine engine, and the mixture is ignited to produce hot combustion gases. The hot gases flow through the combustor assembly and into a turbine where energy is extracted.
Conventional gas turbine engines use a plurality of combustor assemblies. Each combustor assembly includes a fuel injection system, a combustor liner and a transition duct. Combustion occurs in the combustion liner. Hot combustion gases flow through the combustor liner and the transition duct into the turbine.
The combustor liner, transition duct and other components of the gas turbine engine are subject to these hot combustion gases. Current design criteria require that the temperature of the combustor liner be kept within its design parameters by cooling it. One way to cool the combustor liner is impingement cooling a surface wall of the liner.
In impingement cooling of a combustor liner, the front side (inner surface) of the combustor liner is exposed to the hot gases, and a jet-like flow of cooling air is directed towards the backside wall (outer surface) of the combustor liner. After impingement, the “spent air” (i.e. air after impingement) flows generally parallel to the component.
Gas turbine engines may use impingement cooling to cool combustor liners and transition ducts. In such arrangements, the combustor liner is surrounded by a flow sleeve, and the transition duct is surrounded by an impingement sleeve. The flow sleeve and the impingement sleeve are each formed with a plurality of rows of cooling holes.
A first flow annulus is created between the flow sleeve and the combustor liner. The cooling holes in the flow sleeve direct cooling air jets into the first flow annulus to impinge on the combustor liner and cool it. After impingement, the spent air flows axially through the first flow annulus in a direction generally parallel to the combustor liner.
A second flow annulus is created between the transition duct and the impingement sleeve. The holes in the impingement sleeve direct cooling air into the second flow annulus to impinge on the transition duct and cool it. After impingement, the spent air flows axially through the second flow annulus.
The combustor liner and the transition duct are connected, and the flow sleeve and the impingement sleeve are connected, so that the first flow annulus and the second flow annulus create a continuous flow path. That is, spent air from the second flow annulus continues into the first flow annulus. This flow from the second flow annulus creates cross flow effects on cooling air jets of the flow sleeve and may reduce the effectiveness and efficiency of these cooling air jets. For example, flow through the second flow annulus may bend the jets entering through the flow sleeve, reducing the heat transferring effectiveness of the jets or completely preventing the jets from reaching the surface of the combustor liner. This is especially a problem with regard to the first row of flow sleeve cooling holes adjacent the impingement sleeve.